Polyolefin Film and Method for Manufacturing Polyolefin Film

Abstract

A polyolefin film containing a polyolefin, wherein the polyolefin contains polyethylene, a melting point of the polyolefin film is 134° C. or higher and 140° C. or lower, a basis weight-equivalent puncture strength Sm of the polyolefin film is 70 gf/(g/m 2 ) or more and 150 gf/(g/m 2 ) or less, and a shutdown temperature Ts and the Sm of the polyolefin film satisfy the following relationship: Ts<0.13×Sm+130.

1 . A polyolefin film comprising a polyolefin, wherein
 the polyolefin comprises polyethylene,   a melting point of the polyolefin film is 134° C. or higher and 140° C. or lower,   a basis weight-equivalent puncture strength Sm of the polyolefin film is 70 gf/(g/m 2 ) or more and 150 gf/(g/m 2 ) or less, and   a shutdown temperature Ts and the Sm of the polyolefin film satisfy the following relationship:   
       
         
           
             
               Ts 
               < 
               
                 
                   
                     0 
                     . 
                     1 
                   
                   ⁢ 
                   3 
                   × 
                   Sm 
                 
                 + 
                 
                   1 
                   ⁢ 
                   3 
                   ⁢ 
                   
                     0 
                     . 
                   
                 
               
             
           
         
       
     
     
         2 . The polyolefin film according to  claim 1 , wherein a total amount of a side chain having 3 carbon atoms and a side chain having 4 carbon atoms measured for the polyolefin film is 0.1 mol % or less as a proportion to a total number of carbon atoms. 
     
     
         3 . The polyolefin film according to  claim 1 , wherein the polyethylene comprises polyethylene A and polyethylene B different from the polyethylene A, wherein
 the polyethylene A is homopolyethylene having a melting point of 134° C. or higher and 138° C. or lower and a melt index of 0.5 g/10 min or more and 50 g/10 min or less, and   a content of the polyethylene A based on 100 parts by mass in total of the polyethylene A and the polyethylene B is 20 parts by mass or more and 80 parts by mass or less.   
     
     
         4 . The polyolefin film according to  claim 3 , wherein
 the polyethylene B is homopolyethylene having a viscosity average molecular weight of 800,000 or more and 5,000,000 or less, and   a content of the polyethylene B based on 100 parts by mass in total of the polyethylene A and the polyethylene B is 20 parts by mass or more and 80 parts by mass or less.   
     
     
         5 . The polyolefin film according to  claim 1 , wherein a heat shrinkage rate at 120° C. is 10% or less. 
     
     
         6 . The polyolefin film according to  claim 1 , wherein a film thickness-equivalent air permeability Gt and a porosity P of the polyolefin film satisfy the following relationship: 
       
         
           
             
               
                 LN 
                 ⁡ 
                 ( 
                 Gt 
                 ) 
               
               ⁢ 
               
                 ≤ 
                 
                   
                     
                       - 
                       
                         0 
                         . 
                         0 
                       
                     
                     ⁢ 
                     7 
                     ⁢ 
                     0 
                     × 
                     P 
                   
                   + 
                   
                     5 
                     . 
                     8 
                     . 
                   
                 
               
             
           
         
       
     
     
         7 . The polyolefin film according to  claim 3 , wherein a difference in swelling onset temperature between the polyethylene A and the polyethylene B determined by the following measurement is 10° C. or less and is calculated as follows:
 Measurement of swelling onset temperature 
 (Measurement of D 10 , D 50 , and D 90 )
 respective particle diameters of the polyethylene A and the polyethylene B are measured using a laser particle size distribution analyzer with methanol as a dispersion medium; 
 a cumulative particle size distribution from smaller particle sizes is prepared on the basis of the measurement, and particle diameters that attain cumulative percentages of 10%, 50%, and 90% are defined as D 10 , D 50 , and D 90 , respectively, of each polyethylene; 
 
 (Measurement of swelling onset temperature T)
 a swelling onset temperature T 10  of a polyethylene particle having a particle diameter of D 10  is determined as follows: polyethylene particles having a major axis diameter and a minor axis diameter (as for a plane figure of a particle observed under an optical microscope, a distance between parallel lines having the shortest interval is defined as the minor axis diameter of the particle, and a distance between parallel lines having the longest interval in a direction perpendicular thereto is defined as the major axis diameter of the particle) within a range of D 10 ±10% are identified from a particle group of each polyethylene under an optical microscope, and one particle is arbitrarily collected therefrom; 
 the collected one polyethylene particle is loaded onto a glass slide, and 0.05 ml of liquid paraffin is dropped to the polyethylene particle; Then, a glass cover is placed thereon so as to interpose the polyethylene particle; 
 then, the glass slide is loaded onto a heat stage, and the temperature is allowed to increase from room temperature to 150° C. under temperature increase conditions given below; 
 the appearance of the polyethylene particle during temperature increase is photographed every 6 seconds under an optical microscope equipped with a camera; 
 an equivalent circle diameter of the polyethylene particle is calculated from each of the obtained observation images; 
 the lowest temperature at which the equivalent circle diameter of the polyethylene particle has become larger by 1% or more based on the equivalent circle diameter of the polyethylene particle at 80° C. in a temperature range of 80° C. or higher and 150° C. or lower is defined as the swelling onset temperature of the polyethylene particle; 
 measurement is performed at 10 points, and an average value thereof is defined as a swelling onset temperature T 10  of each polyethylene; 
 
 (Temperature increase conditions)
 temperature increase rate from room temperature to 35° C.: 5° C./min, 
 temperature increase rate in a range from 35° C. to 80° C.: 8° C./min, 
 temperature increase rate in a range from 80° C. to 150° C.: 5° C./min; 
 next, a swelling onset temperature T 50  of a polyethylene particle having a particle diameter of D 50 , and a swelling onset temperature T 90  of a polyethylene particle having a particle diameter of D 90  are also determined in the same manner as in the swelling onset temperature T 10  using a collected polyethylene particle having a major axis diameter and a minor axis diameter within a range of D 50 ±10%, and a collected polyethylene particle having a major axis diameter and a minor axis diameter within a range of D 90 ±10%; 
 finally, the swelling onset temperature T of each polyethylene is determined as follows: 
 
 
       
         
           
             
               
                 T 
                 = 
                 
                   
                     
                       T 
                       
                         1 
                         ⁢ 
                         0 
                       
                     
                     + 
                     
                       T 
                       
                         5 
                         ⁢ 
                         0 
                       
                     
                     + 
                     
                       T 
                       
                         9 
                         ⁢ 
                         0 
                       
                     
                   
                   3 
                 
               
               .